NIAMEY, May 6 (Reuters) - Fourteen suspected members of the Nigerian Islamist sect Boko Haram were arrested in neighbouring Niger on Tuesday after an attack on an army patrol in the eastern region of Diffa, the regional governor said.

Diffa, some 1,400 km east of Niger's capital, Niamey, borders the Nigerian state of Borno, the centre of Boko Haram's uprising. Tens of thousands of refugees have fled the fighting to the arid region, and local Niger officials have repeatedly voiced concerns over Boko Haram infiltration.

Yacouba Soumana Gaoh, the regional governor of Diffa, said the army had detained two Boko Haram suspects who had robbed a man at gunpoint early on Tuesday in the commune of Chetimari.

"The security forces then fell into an ambush laid by presumed members of Boko Haram. After fierce fighting, reinforcements were sent in but the attackers were able to cross over the border," he told state television.

The governor said three suspected militants were captured during the fighting, two of whom suffered gunshot wounds. There were no casualties among the army troops, but one of their vehicles was peppered with bullets, he said.

Nine other suspects were later arrested in the regional capital Diffa and the surrounding area, he said.

A military source, who asked not to be identified, told Reuters he was not aware of any link between the arrests and the kidnapping of more than 200 schoolgirls by Boko Haram in northern Nigeria last month. A further eight girls were kidnapped from a village by suspected Boko Haram gunmen on Tuesday.

The kidnappings by the Islamists, who say they are fighting for an Islamic state in Nigeria, have shocked a country long inured to the violence around the northeast and has outraged international opinion.

Officials in neighbouring Chad and Cameroon have strongly denied that Boko Haram had taken the girls across the border into their countries. (Reporting by Abdoulaye Massalaki; Writing by Daniel Flynn; Editing by Bate Felix and Prudence Crowther)